Catalytic material, electrode, and fuel cell using the same

ABSTRACT

A catalytic material and electrode of the present invention are characterized in that the catalyst carrier constituting the above-mentioned catalytic material and electrode includes at least one member selected from the group consisting of nitrogen atoms, oxygen atoms, phosphor atoms, and sulfur atoms. Since the cohesion or growth of catalyst grains can hereby be suppressed, it is possible to provide a highly active catalyst, a high-performance electrode, and a high-output-density fuel cell which uses the same.

FIELD OF THE INVENTION

[0001] The present invention relates to a catalytic material, electrode,and a fuel cell using the Same.

BACKGROUND OF THE INVENTION Related Art

[0002] The problems of global warming and environmental pollution due tomassive consumption of fossil fuels are becoming critical problems inrecent years. Fuel cells powered by hydrogen as countermeasures againstthese problems, including solid-state polymer electrolyte fuel cells(PEFCs), are now catching attention in lieu of the internal-combustionengines that each burn a fossil fuel. Also, information terminalequipment and the like are dimensionally reduced each year by theprogress of electronic technology, and hereby, the rapid proliferationof hand-held electronic equipment is being accelerated. Currently,direct methanol fuel cells (DMFCs) fueled by methanol are underdevelopment as the next generation of power supplies for compensatingfor increases in the volumes of information handled by hand-heldelectronic equipment, and for the increases in power consumption thatare associated with higher-speed information processing.

[0003] The catalytic materials used for the electrodes and othercomponents of these fuel cells generally take a configuration in whichcatalysts are dispersed on catalyst carriers, as disclosed in JapaneseApplication Patent Laid-open Publication No. 2002-83604. Also, catalystcarriers use carbon materials.

SUMMARY OF THE INVENTION

[0004] The activity of catalytic materials greatly depends on theparticle sizes of the catalytic components included in the catalyticmaterial. Decreases in the particle size of the catalytic componentcorrespondingly increase the specific surface area (surface area of thecatalytic component particles/weight of the catalytic componentparticles) of that catalytic component. When identical amounts ofcatalytic components are used, the activity of the catalyst is enhancedsince its active area increases.

[0005] In conventional catalytic materials, however, since therespective catalytic components are supported on catalyst carriersmainly by physical adsorption, the particles of these catalyticcomponents cohere or grow during the preparation of the catalyticmaterials and under the operating environments of cells. Consequently,the particles of the catalytic component increase in size to decrease inspecific surface area. Such cohesion or growth of catalyst grains hasmade it difficult to prepare catalytic components with a small particlesize, or to maintain the particle size of the catalytic component underthe operating environment of the cell at a small value.

[0006] An object of the present invention is to provide a catalyticmaterial, an electrode, and a fuel cell using the same. The fuel celloutputs an improved density by using the electrode that comprises thecatalytic component with a large specific surface area and a smallparticle size.

[0007] The “catalytic components” here refer to a metal or metalliccompound that has catalytic activity, and the “catalyst carriers” aresubstances that support the aforementioned catalysts. Carbon black,carbon nano tubes, or other carbon materials are used in the case ofcatalyst carriers for fuel cells.

DETAILED DESCRIPTION OF THE INVENTION

[0008] A major feature of the invention pertaining to the presentapplication is that in a catalytic material, which includes a catalystcarrier and a catalytic component, the catalyst carrier further includesatoms that can be covalent bonded to the catalytic component. Here,“covalent bond” includes “coordinate bond”.

[0009] Also, the catalyst carrier, if composed mainly of carbon, ispreferred as a catalytic material for a fuel cell.

[0010] Structurally, the “carbon” here includes various substances fromamorphous types to crystalline types such as graphite.

[0011] The “catalyst carrier further includes atoms that can be bondedby covalent bonds” means that atoms which can be bonded by covalentbonds to the catalytic component exist in the catalyst carrier bychemically bonding to the atoms (for example, carbon atoms) thatconstitute the catalyst carrier. If the atoms constituting the catalystcarrier are carbon atoms, however, the crystal particle size of thecarbon crystal can be either large or small or the carbon can beamorphous. Or the atoms that can be bonded by covalent bonds may becovalent bonded to carbon atoms while at the same time being covalentbonded to hydrogen atoms.

[0012] A fuel cell with high output density can be provided by using,for a fuel cell, the catalytic materials of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic view of the carbon which includes thenitrogen pertaining to an embodiment;

[0014]FIG. 2 is a schematic view of the carbon which includes thenitrogen pertaining to another embodiment;

[0015]FIG. 3 is a schematic view of a single-wall carbon nanotube;

[0016]FIG. 4 is a schematic view of a multiple-wall carbon nanotube;

[0017]FIG. 5 is a schematic view of a carbon nanotube including thenitrogen pertaining to a yet another embodiment;

[0018]FIG. 6 is a schematic view of a catalytic material pertaining to astill another embodiment;

[0019]FIG. 7 is a schematic view of a direct methanol fuel cell usingthe electrodes pertaining to a still another embodiment;

[0020]FIG. 8 is a cross-sectional schematic view of an MEA pertaining toa yet another embodiment; and

[0021]FIG. 9 shows a TEM photo of a catalytic material pertaining to ayet another embodiment.

PREFERRED EMBODIMENTS OF THE INVENTION

[0022] Although the methods of preparing a catalytic material, describedbelow, apply to DMFC, the application of the catalytic materialspertaining to the preferred embodiments of the present invention is notlimited to DMFC; any types of catalytic materials can be applied,provided that they take a configuration in which a catalyst is dispersedon a catalyst carrier composed mainly of carbon atoms.

[0023] The “catalytic materials” in these preferred embodiments meanmaterials having a catalytic component supported by a catalyst carrier.

[0024] [Embodiment 1]

[0025] A method of preparing the catalytic material and electrodepertaining to the present embodiment is described below.

[0026] In the present embodiment, nitrogen atoms are used as the atomsthat can be bonded by covalent bonds to a catalytic component.

[0027] Three and a half grams of carbon black containing5-atomic-percent nitrogen, an alkaline solution, and a reducing agentare encased in a container and then mixed for 30 minutes by beingstirred using a stirrer. Here, for example, a potassium hydroxidesolution, a sodium hydroxide solution, aqueous ammonia, or the like canbe used as the alkaline solution. Similarly, sodium borohydride,formalin, or the like can be used as the reducing agent. In the presentembodiment, a potassium hydroxide solution and formalin are used as thealkaline solution and the reducing agent, respectively. A solution of asolution of a catalytic component is added to the mixture includingthese substances, and after the container has been maintained at atemperature of 40° C. using a water bath, the contents of the containerare further stirred for one hour using a stirrer. For example, achloride can be used as the salt of the catalytic component, and in thepresent embodiment, 2.1 grams of chloroplatinic acid is used. Thesolution, after being stirred, is filtered using a glass filter. Next,pure water is added to the thus-obtained substance, and after cleaningand filtering operations have been repeated seven times, the substancethat has been finally obtained is dried in a constant-temperature ovenat 80° C. for two days. After being dried, the substance is crushed in amortar, and hereby, 4.5 grams of catalytic material with platinumsupported on the carbon that includes nitrogen atoms is obtained. Thismaterial can likewise be prepared by using, for example, the alcoholreduction method, instead of the method in the present embodiment.

[0028] A mixture consisting of the obtained 1.0 gram of catalyticmaterial, 0.6 grams of perfluorocarbon sulfonic acid, which is a protonconductive material, and slurry of a water/alcohol (1/4) mixed solvent,is prepared and then an electrode is formed on carbon paper by use ofscreen printing.

[0029] Schematic views of a catalyst carrier pertaining to the presentembodiment are shown in FIGS. 1 and 2. Some of the carbon atoms incarbon are replaced with nitrogen atoms mainly in the two forms of FIGS.1 and 2. FIG. 1 represents a configuration in which carbon atoms 101 arereplaced with nitrogen atoms 102 in the form of pyridine structure. FIG.2 represents a configuration in which carbon atoms 201 are replaced withnitrogen atoms 202 in the form that six-membered-ring structure ismaintained. When the crystal particle size is very small, however, sincethe bonds between the carbon atoms and the nitrogen atoms do not alwaystake the configurations of FIGS. 1 or 2 and since nitrogen atoms may bebonded to carbon atoms present in amorphous carbon orfive-membered-rings may be formed, the present embodiment is not limitedto these conformations.

[0030] Such a catalyst carrier with carbon and nitrogen, can be obtainedby, for example, supplying a C₂H₂/N₂ gas mixture using the chemicalvapor deposition (CVD) method. Or the catalyst carrier described abovecan likewise be obtained by a DC magnetron sputtering method that uses agraphite target under the atmosphere of an argon gas/nitrogen gasmixture. Or the catalyst carrier can likewise be obtained by heating anorganic substance that contains a nitrogen gas, under an argon gasatmosphere.

[0031] Here, the bonds between the nitrogen atoms and the particles ofthe catalytic component are covalent bonds by which the particles of thecatalytic component are stably supported on the surface of the carbon.Therefore, under the status that the carbon that includes nitrogen atomsis used in the catalyst carrier, the particles of the catalyticcomponent have their movements bound by the bonds with the nitrogenatoms. Thereby, the particles of the catalytic component can beprevented from cohering or growing during the preparation of thecatalytic material and under the operating environment of the cell.

[0032] The advantage that the particles of the catalytic component canbe prevented from cohering or growing is valid for both an anodicelectrode and a cathodic electrode.

[0033] In the range that a fuel is sufficiently supplied to thedispersed particles of the catalytic component, it is desirable that theamount of catalytic component supported on the catalyst carrier shouldbe as large as possible.

[0034] For the conventional carbon black used as a catalyst carrier,however, if the amount of support of the catalytic component isincreased too significantly, the particles thereof cohere each other,thus reducing the effective area that is the catalyzing surface area ofthe catalytic component. For this reason, the maximum amount of supportof the catalytic component has been about 50 weight percent (weight ofthe catalytic component/weight of the catalytic material).

[0035] However, since, as described above, the use of a catalyst carrierwhich includes nitrogen atoms causes the movements of the particles ofthe catalytic component to be bound by the covalent bonds with thenitrogen atoms, it is possible to prevent cohesion and to increase theamount of catalytic component supported.

[0036] For the catalytic material prepared in the present embodiment,portions of the catalytic component have the movements of theirparticles bound by covalent bonding to nitrogen atoms while maintaininga small particle size of about 2 nanometers with a certain probability.

[0037] Some of the particles of the catalytic component, however, stillremain in the status that they can obtain thermal energy or the like andmove about. Once these particles of the catalytic component haveapproached nitrogen atoms while moving about, the movements of thoseparticles are bound by covalent bonds, or some of the particles of thecatalytic component may have their movements bound in the neighborhoodof nitrogen atoms after cohesion each other or becoming grown to acertain extent with a certain probability. It is considered that whethersome of the particles of the catalytic component have their movementsbound while maintaining a small particle size or have their movementsbound after cohesion to a certain extent depends on the rate ofdispersion of nitrogen atoms on the catalyst carrier or on the particlesize of the particles of the catalytic component existing during thepreparation of the catalytic material.

[0038] The fact that the particles of the catalytic component can beprevented from cohesion by having their movements bound offers theadvantage that the distance between the particles of the catalyticcomponent can be reduced below the distance obtained using conventionaltechnology. That is to say, even at the conventional distance that makesthe particles of a catalytic component too close to each other and thuscoheres each particle, the use of the catalytic material described inthe present embodiment prevents the cohesion between the adjacentparticles of the catalytic component since the movements of theparticles thereof are bound. Therefore, compared with its conventionalvalue, the amount of catalyst carrier can be reduced when the sameamount of catalytic component is included in an electrode. The fact thatthe amount of catalyst carrier can be reduced means that given the sameelectrode area, the thickness of the electrode can be reduced and herebythat the diffusion of a fuel in the electrode, the conductivity ofelectrons, and the conductivity of protons can be improved. Sincematerials mobility resistance can thus be reduced, the output density ofa membrane electrode assembly (hereinafter, called the MEA804) can beimproved. Also, the output characteristics values of PEFC and DMFC canbe improved by using an MEA higher in output density. In addition,downsizing is possible by fixing these output characteristics values.

[0039] The binding effect of nitrogen atoms with respect to thecatalytic component is provided by the nitrogen atoms existing in thesurface layer of the catalyst carrier. Here, the density of the nitrogenatoms on the surface is dictated by the target amount of catalyticcomponent supported and the particle size thereof. For this reason,although the density is not limited to any specific value, it ispreferable that in the X-ray photoelectron spectroscopic (XPS) densityanalysis of the nitrogen atoms on the surface of the catalyst carrier,the above density should range from about 0.1 to 30 atomic percent. Thisis because, if the density of the nitrogen atoms on the surface of thecatalyst carrier is less than 0.1 atomic percent, the binding effectcannot be easily obtained when supporting a catalyst whose densityexceeds 0.01 weight percent, the value practically required. Or if theabove density is greater than 30 atomic percent, it becomes difficultfor the nitrogen atoms to be stably included in the carbon black whilemaintaining graphite structure, and thereby, the catalyst carrierdecreases in mechanical strength. Also, such stereographic structure asthe structure of a diamond, is created and thus the rate ofgraphite-like structure decreases, with the result that electronconductivity decreases. Further preferable density is from 1 to 10atomic percent.

[0040] Although carbon black is used in the present embodiment as thechief component of the catalyst carrier into which nitrogen atoms are tobe included, since the carbon black consists of secondary particleswhich are a cohered assembly of primary particles ranging from aboutseveral ten to several hundred nanometers in diameter, since the surfaceof the carbon black is rough, and since its specific surface area islarge, it is considered that the number of sites at which the catalystcan be supported, in other words, the number of nitrogen atoms presenton the surface of the catalyst carrier in the present embodiment, isgreat and hereby that the amount of support of the catalytic componentper unit volume can be increased.

[0041] Therefore, it is considered from the above description that thethickness of the electrode can, in turn, be reduced and hereby that thediffusion of a fuel and the electro-conductivity of electrons andprotons can be enhanced. Also, costs can be minimized since, in general,carbon black is easy to produce.

[0042] In order to evaluate the electrode that has been createdaccording to the present embodiment, an electrode that uses carbon notincluding nitrogen atoms, instead of the carbon that includes nitrogenatoms, has been created as comparative example 1 by using a methodsimilar to that of embodiment 1.

[0043] The electrode of embodiment 1 and the electrode of comparativeexample 1 have been immersed in a methanol-containing electrolyticsolution [1.5 M sulfuric acid (M short for “mol/l”) and20-weight-percent methanol]] and monopolar measurements (current/voltagemeasurements) have been conducted. Here, a saturated-calomel electrodehas been used as a reference electrode, and a metallic plate has beenused as its counter electrode.

[0044] As a result, with the electrode of embodiment 1, a currentdensity about 1.2 times that of the case of the electrode shown incomparative example 1 has been obtained at the same potential, and it isthus considered that the electrode of embodiment 1 is higher inperformance.

[0045] [Embodiment 2]

[0046] It is to be understood that the second embodiment described belowis the same as the method of embodiment 1, except that a mixture, inwhich the density of a carbon nanotube (hereinafter, called “CNT”) thatincludes 5-atomic-percent nitrogen atoms is 80 weight percent withrespect to the density of 20-weight-percent carbon black which includes5-atomic-percent nitrogen atoms, has been used.

[0047] When a plurality of CNTs are used, since each CNT has a pluralityof contact points and comes into contact, the resistivity inside theelectrode can be reduced.

[0048] The CNTs pertaining to the present embodiment are shown in FIGS.3 and 4. FIG. 3 shows a CNT having a cylindrical graphene sheet 301, andthis type of CNT is called the single-wall carbon nanotube (SWCNT). FIG.4 shows a CNT having an outer graphene sheet 401 and an inner graphenesheet 402 positioned inside the graphene sheet 401, and this type of CNTis called the multiple-wall carbon nanotube (MWCNT).

[0049] MWCNT, as its name implies, does not always have two walls andcan has three or more walls.

[0050] Also, both SWCNT and MWCNT may be covered with a five-fold-ringsemispherical cap, which is alias called the fullerene cap.

[0051] In addition, the graphene sheet, called the carbon nanofiber, maynot be parallel with respect to the longitudinal direction of the tube,and this type of graphene sheet can be used alternatively.

[0052] Since, in general, SWCNT is large in specific surface area, ithas the advantage that there are a number of sites at which the catalystcan be supported, whereas MWCNT has the advantages that it is high inelectron conductivity, and hence, low in the loss of electron migration.

[0053] The CNT that includes nitrogen atoms pertaining to the presentembodiment is shown in FIG. 5. Nitrogen atoms 502 are doped in such aconformation that they are replaced with the carbon atoms 501constituting the CNT.

[0054] A schematic view of a catalytic material pertaining to thepresent embodiment is shown in FIG. 6. A catalytic component 602 issupported in particle form on a CNT 601 which includes nitrogen atoms.The catalytic component 602 is supported near the nitrogen atomsincluded in the nitrogen-containing CNT 601. At these locations, themovements of the particles in the catalytic component 602 are bound.Since the CNT 601 that includes nitrogen atoms is high in electronconductivity and has fiber structure, this CNT can become a goodelectron conduction path in an electrode. It is desirable that thecatalytic component 602 be either a single metal selected from a groupconsisting of manganese, iron, cobalt, nickel, ruthenium, rhodium,palladium, rhenium, osmium, iridium, and platinum, or a compoundcomposed of more than at least one type of metal selected from thisgroup. The catalytic component 602 should be, further desirably, amaterial obtained by alloying these metals.

[0055] Platinum is preferable as the catalytic component to be used forthe anode or cathode of a fuel cell. However, when carbon monoxide ispresent or when methanol is to be oxidized, higher performance can beachieved by using platinum and ruthenium in the catalytic component.Performance close to the desired performance can be provided bycombining platinum, ruthenium, manganese, iron, cobalt, nickel, rhodium,palladium, rhenium, osmium, and iridium, instead of combining platinumand ruthenium.

[0056] In general, an alloy consisting of platinum and ruthenium isdesirable as the catalytic component when it is to be used for an anodicelectrode, and platinum is desirable when the catalytic component is tobe used for a cathodic electrode.

[0057] Comparative example 1 and embodiment 2 have been compared using amethod similar to that of embodiment 1. As a result, with the electrodeof embodiment 2, a current density about 1.5 times that of the case ofthe electrode shown in comparative example 1 has been obtained at thesame potential, and it is thus considered that the electrode ofembodiment 2 is higher in performance.

[0058] [Embodiment 3]

[0059] A third embodiment is the same as comparative example 1, exceptthat 2.1 grams of chloroplatinic acid and 1.1 grams of rutheniumchloride have been used as the salt of the catalytic component.

[0060] The electrode that has been used in comparative example 2 is thesame as that of comparative example 1, except that 2.1 grams ofchloroplatinic acid and 1.1 grams of ruthenium chloride have been usedas the salt of the catalytic component.

[0061] The results of observation of the catalytic material inembodiment 3 and the catalytic material in comparative example 2 by useof a transmission-type electron microscope are shown in FIG. 9. Theaverage particle size of the catalytic component in comparative example2 is about 5 nanometers, and the average particle size of the catalystin embodiment 3 is about 2 nanometers. It can therefore be seen that thecatalyst particles in embodiment 3 are supported in a more finelystructured condition.

[0062] Monopolar measurements have been performed on the electrode ofembodiment 3 and that of comparative example 3 by using a method similarto that of embodiment 1. As a result, with the electrode of embodiment3, a current density about 3 times that of the case of the electrodeshown in comparative example 2 has been obtained at the same potential,and it has thus been found that the electrode of embodiment 3 is higherin performance.

[0063] It has been seen, therefore, that combining platinum andruthenium, instead of using platinum alone, is likewise effective forcreating a catalytic component. An equal effect has also been obtainedby combining platinum and manganese or combining platinum and iron orthe like.

[0064] Also, there are various types of metals such as platinum,ruthenium, manganese, and iron. These metals range from a type presentalone on a catalyst carrier, to a type present as an alloy. In addition,these metals can each be some type of compound. For example, they can beoxides or chlorides.

[0065] [Embodiment 4]

[0066] A cross-sectional schematic view of the MEA804 pertaining to afourth embodiment is shown in FIG. 8. Although, in FIG. 8, thethicknesses of electrodes and of an electrolyte membrane are depicted inenlarged form for the ease of understanding, the MEA actually created isof a sheet-like shape and has a thickness from about 70 to 500 microns(10 to 100 microns in electrode thickness and 50 to 300 microns inelectrolyte membrane thickness), and the MEA pertaining to the presentembodiment is 100 microns thick. The MEA pertaining to the presentembodiment consists of an anodic electrode 801, a cathodic electrode802, and an electrolyte membrane 803 which is positioned in between bothelectrodes. Next, a method of preparing the MEA804 pertaining to thepresent embodiment is described below.

[0067] The MEA804 is prepared by using the electrode of embodiment 3 asan anodic electrode, and the electrode of embodiment 1 as a cathodicelectrode, then arranging both electrodes on both sides of, andadjacently to, a perfluorosulfonic acid membrane which is to be used asthe electrolyte membrane 803, and thermally crimping and copying thethus-configured object by means of a hot press.

[0068] The method of preparing an MEA, described as comparative example4 below, is same as that of embodiment 4, except that the electrode ofcomparative example 3 and the electrode of comparative example 1 areused as an anodic electrode and a cathodic electrode, respectively.

[0069] A schematic view of the DMFC pertaining to the present embodimentis shown in FIG. 7. The foregoing DMFC consists mainly of an MEA whichis further compose of an anodic electrode 701, a cathodic electrode 703,and a proton-conductive electrolyte membrane 702 positioned in betweenboth electrodes. A fuel 705 composed mainly of methanol and water, issupplied to the anodic electrode 701, and carbon dioxide and water 706are discharged therefrom. A gas 707 that contains air or oxygen, issupplied to the cathodic electrode 703, and an exhaust gas 708 thatcontains water and the unreacted gas within the introduced gas, isdischarged. Also, the anodic electrode 701 and the cathodic electrode703 are connected to an external circuit 704.

[0070] The MEA of the present embodiment and the MEA of comparativeexample 4 have been used in the DMFC of such configuration as describedabove, and both MEAs have been compared in output density. It isconsidered that compared with the output density of the DMFC which usesthe MEA of comparative example 4, the output density of the DMFC usingthe MEA of the present embodiment is about two times.

[0071] [Embodiment 5]

[0072] Since the catalyst-binding effect of nitrogen atoms dependsmainly on the nitrogen atoms existing on the surface of a catalystcarrier, an equal effect can be obtained by using, for a catalystcarrier, a substance structured so that the surface of carbon black iscovered with the carbon which includes nitrogen atoms. In this case,since the shape of the catalyst carrier depends on the shape of theemployed carbon black to a certain extent, there is the advantage thatthe final shape of the catalyst carrier can be selected by selecting theshape of the carbon black to be actually used.

[0073] A method of preparation is described below. Carbon black andhexamethoxymethyl melamine have been mixed at a weight ratio of 1:4 inethanol for one hour and then this mixture has been dried in theatmosphere for 24 hours at 80° C. The thus-obtained object has beenburned for one hour at 800° C. under an argon atmosphere, with theresult that a catalyst carrier in which the surface of the carbon blackis covered with the carbon which includes nitrogen atoms has beenobtained.

[0074] The obtained catalyst carrier has been analyzed with XPS to findthat the density content of the nitrogen atoms is 5 atomic percent. Acatalytic material has been obtained using a method similar toembodiment 3, except that the above substance has been used instead ofthe carbon including 5-atomic-percent nitrogen.

[0075] The catalytic material in the present embodiment and thecatalytic material in comparative example 2 have been observed using atransmission-type electron microscope to find that the average particlesize of the catalytic component supported by the catalytic materialwhich has been obtained in the present embodiment is about 2 nanometers,and this indicates that the catalytic component in the presentembodiment is supported in a more finely structured particle condition.

[0076] [Embodiment 6]

[0077] A catalytic material with a catalyst supported on the carbonwhich includes nitrogen atoms can likewise be obtained by previouslymixing the salt of the catalytic component and a precursor of the carbonwhich includes nitrogen atoms, and then burning the mixture.Zero-point-three grams of phenylene diamine, 0.7 grams of polyamic acid,100 ml of N-methyl-2-pyrrolidinone, 0.2 grams of chloroplatinic acid,and 0.1 gram of ruthenium chloride are mixed and then stirred for onehour. The stirred mixture is then vacuum-dried for two hours at 200° C.The thus-obtained solid substance is burned at 800° C. for one hourunder an argon atmosphere.

[0078] The catalytic material in embodiment 6 and the catalytic materialin comparative example 2 have been observed using a transmission-typeelectron microscope to find that the particle sizes of the catalysts arealmost the same (approximately 5 nanometers). It is considered, however,that the catalyst in embodiment 6 is dispersed more uniformly.

[0079] [Embodiment 7]

[0080] It is to be understood that the present embodiment is the same asembodiment 3, except that carbon containing 5 atomic % of sulfur that iscapable of bonding to the catalytic component by covalent bond was usedinstead of carbon containing 5 atomic % of nitrogen.

[0081] The electrodes of the present embodiment and those of comparativeexample 6 are measured using a monopolar measuring method similar tothat of embodiment 1. Here, a saturated-calomel electrode is used as areference electrode, and a metallic plate is used as its counterelectrode. As a result, with the electrodes of the present embodiment,current densities about 3 times those of the electrodes shown incomparative example 2 have been obtained at the same potential, and itis thus considered that the electrodes in the present embodiment arehigher in performance.

[0082] The catalytic material in the present embodiment and thecatalytic material in comparative example 2 have been observed using atransmission-type electron microscope to find that the particles of thecatalyst in the present embodiment are supported in a more finelystructured condition.

[0083] [Embodiment 8]

[0084] It is to be understood that this embodiment is the same asembodiment 7, except that a catalyst carrier which includes oxygen atomsin lieu of a catalyst carrier which includes sulfur atoms.

[0085] Single electrode measurements have been performed on theelectrodes of the present embodiment and those of comparative example 2by using a method similar to that of embodiment 1. As a result, with theelectrodes of the present embodiment, current densities about 3 timesthose of the electrodes shown in comparative example 2 have beenobtained at the same potential, and it has thus been found that theelectrodes in the present embodiment are higher in performance. It hasbeen seen, therefore, that using a catalyst carrier which includesoxygen atoms, instead of using a catalyst carrier which includes sulfuratoms, creates an equal effect. It is considered that an equal effectcan also be obtained by using a catalyst carrier which includesphosphorus atoms.

What is claimed is:
 1. A catalytic material comprising a catalyticcomponent and a catalyst carrier for supporting said catalyticcomponent; wherein the catalyst carrier contains atoms that can be ableto form covalent bonds with said catalytic component.
 2. The catalyticmaterial according to claim 1, wherein said catalyst carrier containscarbon.
 3. A catalytic material comprising a catalytic component and acatalyst carrier which comprises carbon; wherein said catalyst carrierhas a structure in which part of the carbon atoms is replaced with atomsthat can be able to form covalent bonds with said catalytic component.4. The catalytic material according to claim 1, wherein said catalyticcomponent is platinum or a platinum compound.
 5. The catalytic materialaccording to claim 1, wherein said catalytic component is at least onemember selected from the group consisting of platinum, ruthenium andtheir compounds.
 6. The catalytic material according to claim 1, whereinsaid catalytic component is at least one member selected from the groupconsisting of platinum, ruthenium, manganese, iron, cobalt, nickel,rhodium, palladium, rhenium, and iridium, and their compounds.
 7. Acatalytic material comprising a catalytic component and a catalystcarrier for supporting said catalytic component; wherein said catalystcarrier further contains a catalytic component and at least one memberselected from the group consisting of nitrogen atoms, oxygen atoms,phosphor atoms, and sulfur atoms.
 8. A membrane/electrode assembly inwhich at least one of an anodic electrode for oxidizing a fuel and acathodic electrode for reducing oxygen has the catalytic material ofclaim 1 and a proton-conductive material and in which aproton-conductive electrolyte membrane is formed between said anodicelectrode and said cathodic electrode.
 9. A fuel cell having an anodicelectrode and a cathodic electrode formed via an electrolyte membrane,said fuel cell further comprising the membrane/electrode assemblydefined in claim
 8. 10 A fuel cell comprising an anodic electrode foroxidizing a liquid fuel, a cathodic electrode for reducing oxygen, andan electrolyte membrane formed between said anodic electrode and saidcathodic electrode; wherein either said anodic electrode or cathodicelectrode or both have a catalytic material in which a catalyst carrierfor supporting a catalytic component and said catalytic component arecontained and in which said catalyst carrier contains atoms that can beable to form covalent bonds with said catalytic component.
 11. A fuelcell comprising an anodic electrode for oxidizing a liquid fuel, acathodic electrode for reducing oxygen, and an electrolyte membraneformed between said anodic electrode and said cathodic electrode;wherein at least one of said anodic electrode and the cathodic electrodehas a catalytic material which contains a carbon-containing catalystcarrier and a catalytic component, said catalyst carrier containing atleast one atom selected from the group of nitrogen, sulfur, oxygen, andphosphor atoms.